Clinical findings and genetic screening for copy number variation mutations in a cohort of South African patients with Parkinson’s disease

Abstract

BACKGROUND. Parkinson’s disease (PD), with a prevalence of up to 4% in Western countries, appears to be less common in Africa, possibly in part because of genetic factors. African studies investigating the genetic causation of PD are limited. OBJECTIVE. To describe the clinical and genetic findings in a group of black South African patients with PD. METHODS. All black African patients with PD from a tertiary hospital neurology clinic were examined. Symptoms were scored according to the Unified Parkinson’s Disease Rating Scale (UPDRS), and patients were classified according to motor features. Genomic DNA was extracted and multiplex ligation-dependent probe amplification was used for detection of copy number variation (CNV) mutations in the known PD-causing genes. RESULTS. Sixteen patients were identified (ages 56 - 82 years). Three had a family history of PD. Classification into motor subtypes showed 44% mixed, 31% akinetic-rigid, and 25% tremor-dominant subtypes. UPDRS scores ranged from 7 to 88, with dementia in 20%. No patient had G2019S LRRK2 and A30P SNCA mutations, and all except one had no CNV mutations in the known PD-causing genes. A female patient (age of onset 50 years, no family history) had a parkin gene heterozygous deletion of exon 4. She had hyperreflexia, bilateral Hoffmann’s reflexes, normal plantar responses and no dystonia. CONCLUSION. This group of black African patients showed similar characteristics to patients in Western studies, possibly with a higher proportion having tremor-dominant disease. Genetic analysis showed one parkin gene mutation. The limited knowledge on PD-causing genes and mutations in black populations warrants further studies involving next-generation sequencing approaches.